CONTRIBUTION TO A UTILITARIAN CLASSIFICATION OF GYPSIFEROUS SOIL

Gypsiferous soils are soils that contain sufficient CaSO4 . 2H(2)O to influence soil physical and chemical properties and to affect plant gr owth and crop production. They cover some 100 million ha, and are part of extensive irrigation schemes in and and semi arid areas in the Mid dle East, Central Asia and Australia. Major world soil classification systems identify and group gypsiferous soils mainly on the basis of pe dogenetic criteria, with comparatively little attention paid to land u se potential and management, Hence, application of new land use classi fications in the field is not always evident, and it may happen that s oils with completely different agricultural potentials are still class ified in one and the same pedologic unit. In this paper the main facto rs that affect genesis, properties and land use potential of gypsifero us soils are critically reviewed, and a number of them identified as d iagnostic criteria for a more pragmatic and user-oriented classificati on, Those criteria include: a more precise definition of the gypsic ho rizon and of gypsum contents, nature of gypsum accumulation, field tex ture, and thickness of soil above the gypsic horizon.